U.S. patent application number 15/780701 was filed with the patent office on 2019-01-03 for electrically conductive tire sealant for puncture detection.
This patent application is currently assigned to Bridgestone Americas Tire Operations, LLC. The applicant listed for this patent is Bridgestone Americas Tire Operations, LLC. Invention is credited to Sheel P. AGARWAL, Terence E. WEI.
Application Number | 20190001761 15/780701 |
Document ID | / |
Family ID | 59057855 |
Filed Date | 2019-01-03 |
United States Patent
Application |
20190001761 |
Kind Code |
A1 |
AGARWAL; Sheel P. ; et
al. |
January 3, 2019 |
ELECTRICALLY CONDUCTIVE TIRE SEALANT FOR PUNCTURE DETECTION
Abstract
Tires having an electrically conductive tire sealing material
containing metallic electrically conductive particles are described
for detecting the presence of one or more sealed puncture areas in
the tire. The tires can have a sealed tire portion that is formed
by the electrically conductive tire sealing material flowing into
and filling a puncture in the tire. The sealed tire portion
includes a portion having electrically conductive particles and the
portion being at the outer surface of the tire such as in the tread
area. The tire can be positioned to be in contact with a conductive
section of an apparatus capable of measuring electrical
conductivity.
Inventors: |
AGARWAL; Sheel P.; (Solon,
OH) ; WEI; Terence E.; (Copley, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bridgestone Americas Tire Operations, LLC |
Nashville |
TN |
US |
|
|
Assignee: |
Bridgestone Americas Tire
Operations, LLC
Nashville
TN
|
Family ID: |
59057855 |
Appl. No.: |
15/780701 |
Filed: |
December 1, 2016 |
PCT Filed: |
December 1, 2016 |
PCT NO: |
PCT/US16/64428 |
371 Date: |
June 1, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62267958 |
Dec 16, 2015 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29D 30/0685 20130101;
B60C 19/08 20130101; B29C 73/163 20130101; B60C 19/122
20130101 |
International
Class: |
B60C 19/08 20060101
B60C019/08; B60C 19/12 20060101 B60C019/12 |
Claims
1-15. (canceled)
16. A pneumatic tire comprising: the tire having an outer surface;
an electrically conductive tire sealing material arranged in an
interior portion of the tire, the sealing material underlying the
outer surface of the tire, the sealing material comprising
electrically conductive metallic particles; wherein a puncture of
the outer surface of the tire that contacts the sealing material is
sealed by the sealing material flowing in the puncture to form a
sealed tire area comprising a portion the sealing material, the
sealed tire area being present at the outer surface of the tire,
and a portion of the electrically conductive metallic particles of
the sealing material being present in the sealed tire area at the
outer surface of the tire.
17. The pneumatic tire of claim 16, the electrically conductive
metallic particles being present in the range of 0.1 to 10 weight
percent of the total weight of the sealing material in the
tire.
18. The pneumatic tire of claim 16, the electrically conductive
metallic particles not being carbon black particles, wherein the
electrically conductive metallic particles are selected from the
group consisting of nickel, copper, zinc, tin, iron, aluminum,
silver, brass, silver coated copper, silver coated nickel, silver
coated aluminum, silver coated tin, silver coated gold, nickel
coated copper, nickel coated silver, metal coated glass, ceramics,
plastics, elastomers, and mica, and combinations thereof.
19. The pneumatic tire of claim 16, the electrically conductive
metallic particles being nanoparticles, the nanoparticles having an
average particle diameter in the range of 5 nanometers to 100
nanometers.
20. The pneumatic tire of claim 16, the sealed tire area being
substantially air tight to prevent leakage of air inside the
pneumatic tire through or around the sealed tire area.
21. The pneumatic tire of claim 16, the sealed tire area at the
outer surface of the tire having a greater average concentration of
electrically conductive metallic particles than the average
concentration of electrically conductive particles over the
remaining outer surface of the tire.
22. The pneumatic tire of claim 16, the electrically conductive
tire sealing material being free of silica.
23. The pneumatic tire of claim 16, the outer surface of the tire
having a tread portion and a sidewall portion, the tread portion
and the sidewall portion having an average electrical conductivity
lower than the electrical conductivity of the electrically
conductive tire sealing material.
24. The pneumatic tire of claim 16, the electrically conductive
sealing material being a layer positioned under a rubber tread area
in a crown portion of the tire, the rubber tread forming a
ground-contacting portion of the outer surface.
25. A method of detecting the presence of a sealed puncture in a
pneumatic tire, the method comprising: positioning the tire to
contact a sensor of an apparatus for detecting electrical
conductivity, the tire comprising an outer surface and an
electrically conductive tire sealing material comprising
electrically conductive particles, a portion of the sealing
material arranged in an interior portion of the tire underlying the
outer surface of the tire and a portion of the sealing material
forming a sealed tire area at the outer surface of the tire;
operating the apparatus to measure the electrical conductivity in
the sealed tire area at the outer surface of the tire; and
comparing the measured electrical conductivity in the sealed tire
area to a baseline electrical conductivity value to determine the
presence of a sealed puncture in the tire, wherein when the
measured electrical conductivity in the sealed tire area is greater
than the baseline electrical conductivity value the tire contains a
sealed puncture.
26. The method of claim 25, the electrically conductive particles
of the electrically conductive tire sealing material being metallic
particles, the electrically conductive metallic particles being
present up to 10 weight percent of the total weight of the sealing
material in the tire, wherein the electrically conductive metallic
particles of the electrically conductive tire sealing material are
selected from the group consisting of nickel, copper, zinc, tin,
iron, aluminum, silver, brass, silver coated copper, silver coated
nickel, silver coated aluminum, silver coated tin, silver coated
gold, nickel coated copper, nickel coated silver, metal coated
glass, ceramics, plastics, elastomers, and mica, and combinations
thereof.
27. The method of claim 25, the outer surface of the tire
comprising a rubber tread and a rubber sidewall, the rubber tread
forming a ground-contacting portion of the outer surface, and the
sealed tire area at the outer surface of the tire having a greater
electrical conductivity than the average electrical conductivity of
the rubber tread and the rubber sidewall of the outer surface of
the tire.
28. The method of claim 27, the electrically conductive tire
sealing material in the tire having a greater electrical
conductivity than the average electrical conductivity of the rubber
tread and the rubber sidewall of the outer surface of the tire.
29. The method of claim 27, the electrically conductive sealing
material being a layer positioned under the rubber tread of the
tire.
30. The method of claim 25, the sealed tire area being formed by
the sealing material flowing in an open puncture, the open puncture
extending from the outer surface of the tire to the sealing
material underlying the outer surface of the tire, the sealing
material flows and fills the open puncture to create the sealed
puncture and the sealed tire area at the outer surface of the
tire.
31. The pneumatic tire of claim 16, the electrically conductive
metallic particles comprising a metal surface.
32. The pneumatic tire of claim 31, the metal surface comprising a
metal selected from the group consisting of nickel, copper, zinc,
tin, iron, aluminum, silver, brass, silver coated copper, silver
coated nickel, silver coated aluminum, silver coated tin, silver
coated gold, nickel coated copper, nickel coated silver, metal
coated glass, and combinations thereof.
33. The pneumatic tire of claim 32, the electrically conductive
tire sealing material further comprising a reinforcing agent, the
reinforcing agent comprising carbon black, zinc oxide, aluminum
hydrate, lithopone, whiting, clays, hydrated silicas, calcium
silicates, silicoaluminates, magnesium oxide, magnesium carbonate,
and combinations thereof.
34. The pneumatic tire of claim 16, the electrically conductive
tire sealing material comprising less than 2 phr of non-metal
electrically conductive particles.
35. The pneumatic tire of claim 34, the non-metal electrically
conductive particles comprising carbon black or silica.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to pneumatic tires having an
electrically conductive tire sealant material for sealing a
puncture, and more particularly, pneumatic tires having a
detectable sealed tire area formed from the electrically conductive
tire sealant material for identifying a punctured tire.
BACKGROUND
[0002] Tires are generally still operable after a puncture because
an object that passes through a tire often does not easily come out
and air does not leak rapidly from the tire. However, over a long
period of run time, the object is exposed to centrifugal forces
caused by the rotation of the tire that can dislodge the object.
When the object comes out, air quickly leaks from the tire and
operation of a vehicle can become dangerous. To combat punctures,
modern puncture-sealing pneumatic tires provide a sealant material
that prevents the leakage of air when a foreign object, for
example, a nail on a roadway surface, penetrates through the tire
during operation.
[0003] The sealant layer is often formed of a thin viscous rubber
layer adhered integrally to an inner peripheral surface of the tire
at the backside of the tread portion. When a foreign object falls
out of a puncture and forms an opening, the same centrifugal forces
caused by the rotation of the tire that dislodged the object forces
the viscous sealant layer to flow into the puncture opening. The
sealant layer fills and preferably closes the puncture opening to
result in the tire being air-tight for continued use.
[0004] A tire having a sealed puncture can continue to be used
without the puncture area being noticed by a driver. That is, an
effective sealant layer can close a puncture opening to form an
air-tight seal undetected by a driver. Often, the sealed area or
leak can sometimes only be detected after dismounting the tire and
performing an inspection. There is an interest, however, that a
sealed puncture be detected to notify the driver of a possible
defect, preferably without having to dismount a tire from a rim. It
is an objective of the present disclosure to overcome one or more
difficulties related to the prior art. It has been found that an
electrically conductive tire sealant material can be used to detect
a sealed puncture, for instance, on the outer surface of the tire
and that an external apparatus can be used to indicate such a
sealed puncture. The sealed puncture can be detected without
dismounting the tire, which leads to a quick and cost effective
method for notifying a driver of a puncture.
SUMMARY
[0005] In a first aspect, there is a pneumatic tire that includes
an outer surface; an electrically conductive tire sealing material
arranged in an interior portion of the tire, the sealing material
underlies the outer surface of the tire, the sealing material
contains electrically conductive metallic particles; wherein a
puncture of the outer surface of the tire that contacts the sealing
material is sealed by the sealing material flowing in the puncture
to form a sealed tire area including a portion the sealing
material, the sealed tire area is present at the outer surface of
the tire, and a portion of the electrically conductive metallic
particles of the sealing material are present in the sealed tire
area at the outer surface of the tire.
[0006] In an example of aspect 1, the electrically conductive
metallic particles are present up to 10 weight percent of the total
weight of the sealing material in the tire.
[0007] In another example of aspect 1, the electrically conductive
metallic particles are present in the range of 0.1 to 5 weight
percent of the total weight of the sealing material in the
tire.
[0008] In another example of aspect 1, the electrically conductive
metallic particles do not include carbon black particles.
[0009] In another example of aspect 1, the electrically conductive
metallic particles are selected from the group of nickel, copper,
zinc, tin. iron, aluminum, silver, brass, silver coated copper,
silver coated nickel, silver coated aluminum, silver coated tin,
silver coated gold; nickel coated copper, nickel coated silver;
metal coated: glass, ceramics, plastics, elastomers, and mica, and
combinations thereof.
[0010] In another example of aspect 1, the electrically conductive
metallic particles are nanoparticles.
[0011] In another example of aspect 1, the electrically conductive
metallic particles have an average particle diameter in the range
of 5 nanometers to 100 nanometers.
[0012] In another example of aspect 1, the sealed tire area is
substantially air tight to prevent leakage of air inside the
pneumatic tire through or around the sealed tire area.
[0013] In another example of aspect 1, the sealed tire area at the
outer surface of the tire has a greater average concentration of
electrically conductive metallic particles than the average
concentration of electrically conductive particles or electrically
conductive metallic particles over the remaining outer surface of
the tire.
[0014] In another example of aspect 1, the electrically conductive
tire sealing material is free of silica.
[0015] In another example of aspect 1, the outer surface of the
tire has a tread portion and a sidewall portion, the tread portion
and the sidewall portion each has an average electrical
conductivity lower than the electrical conductivity of the
electrically conductive tire sealing material.
[0016] In another example of aspect 1, the electrically conductive
sealing material is a layer positioned under a tread area in a
crown portion of the tire.
[0017] The first aspect may be provided alone or in combination
with any one or more of the examples of the first aspect discussed
above.
[0018] In a second aspect, there is a pneumatic tire that includes
a tire that has an outer surface, the outer surface includes a
rubber tread and a rubber sidewall, the rubber tread forms a
ground-contacting portion of the outer surface; an electrically
conductive tire sealing layer arranged in an interior portion of
the tire, the sealing layer underlies the outer surface of the tire
and the sealing layer includes electrically conductive metallic
particles; wherein the electrically conductive tire sealing layer
has a greater electrical conductivity than the average electrical
conductivity of the rubber tread and the rubber sidewall forming
the outer surface of the tire.
[0019] In an example of aspect 2, the electrically conductive
metallic particles are selected from the group of nickel, copper,
zinc, tin, iron, aluminum, silver, brass, silver coated copper,
silver coated nickel, silver coated aluminum, silver coated tin,
silver coated gold; nickel coated copper, nickel coated silver;
metal coated: glass, ceramics, plastics, elastomers. and mica, and
combinations thereof.
[0020] In another example of aspect 2, the electrically conductive
metallic particles are present in the range of 0.1 to 5 weight
percent of the total weight of the sealing layer in the tire.
[0021] In another example of aspect 2, the electrically conductive
sealing layer is positioned under the rubber tread of the tire.
[0022] The second aspect may be provided alone or in combination
with any one or more of the examples of the second aspect discussed
above, or with any one or more of the examples of the first
aspect.
[0023] In a third aspect, there is a method of detecting the
presence of a sealed puncture in a pneumatic tire, the method
includes positioning the tire to contact a sensor or probe of an
apparatus for detecting electrical conductivity, the tire includes
an outer surface and an electrically conductive tire sealing
material containing electrically conductive particles, a portion of
the sealing material is arranged in an interior portion of the tire
that underlies the outer surface of the tire and a portion of the
sealing material forms a sealed tire area at the outer surface of
the tire; operating the apparatus to measure the electrical
conductivity in the sealed tire area at the outer surface of the
tire; and comparing the measured electrical conductivity in the
sealed tire area to a baseline electrical conductivity value to
determine the presence of a sealed puncture in the tire, wherein
when the measured electrical conductivity in the sealed tire area
is greater than the baseline electrical conductivity value the tire
contains a sealed puncture.
[0024] In an example of aspect 3, the electrically conductive
particles of the electrically conductive tire sealing material are
metallic particles, the electrically conductive metallic particles
are present up to 10 weight percent of the total weight of the
sealing material in the tire.
[0025] In another example of aspect 3, the electrically conductive
metallic particles of the electrically conductive tire sealing
material are selected from the group of nickel, copper, zinc, tin,
iron, aluminum, silver, brass, silver coated copper, silver coated
nickel, silver coated aluminum, silver coated tin, silver coated
gold; nickel coated copper, nickel coated silver; metal coated:
glass, ceramics, plastics, elastomers. and mica, and combinations
thereof.
[0026] In another example of aspect 3, the outer surface of the
tire includes a rubber tread and a rubber sidewall, the rubber
tread forms a ground-contacting portion of the outer surface, and
the sealed tire area at the outer surface of the tire has a greater
electrical conductivity than the average electrical conductivity of
either the rubber tread or the rubber sidewall forming the outer
surface of the tire.
[0027] In another example of aspect 3, the electrically conductive
tire sealing material in the tire has a greater electrical
conductivity than the average electrical conductivity of the rubber
tread and the rubber sidewall of the outer surface of the tire.
[0028] In another example of aspect 3, the electrically conductive
sealing material is a layer positioned under the rubber tread of
the tire.
[0029] In another example of aspect 3, the sealed tire area at the
outer surface of the tire is in a tread portion of the tire.
[0030] In another example of aspect 3, the sealed tire area is
formed by the sealing material flowing in an open puncture, the
open puncture extends from the outer surface of the tire to the
sealing material that underlies the outer surface of the tire, the
sealing material flows and fills the open puncture to create the
sealed puncture and the sealed tire area at the outer surface of
the tire.
[0031] The third aspect may be provided alone or in combination
with any one or more of the examples of the third aspect discussed
above, or with any one or more of the examples of the first or
second aspects.
[0032] The accompanying drawings are included to provide a further
understanding of principles of the invention, and are incorporated
in and constitute a part of this specification. The drawings
illustrate one or more embodiment(s), and together with the
description serve to explain, by way of example, principles and
operation of the invention. It is to be understood that various
features disclosed in this specification and in the drawings can be
used in any and all combinations. By way of non-limiting example
the various features may be combined with one another as set forth
in the specification as aspects.
DETAILED DESCRIPTION
[0033] The terminology as set forth herein is for description of
the embodiments only and should not be construed as limiting the
invention as a whole.
[0034] Herein, when a range such as 5-25 (or 5 to 25) is given,
this means preferably at least or more than 5 and, separately and
independently, preferably not more than or less than 25. In an
example, such a range defines independently at least 5, and
separately and independently, not more than 25.
[0035] The term "phr" means parts per hundred parts of rubber by
weight, and is a measure common in the art wherein components of a
composition (e.g., sealant material) are measured relative to the
total of all of the elastomer (rubber) components. The total phr or
parts for all rubber components, whether one, two, three, or more
different rubber components are present in a rubber composition are
defined as 100 phr. Other non-rubber components are generally
proportional to the 100 parts of rubber and the relative amounts
may be expressed in phr.
[0036] The present disclosure relates to an electrically conductive
tire sealing material or sealant material, used interchangeably
herein, for use in tires. The sealing material has a relatively
high viscosity and is desirably not significantly influenced by
heat, and therefore the material can be generally free from flowing
and accumulation during running, even when a cover layer or a flow
preventing wall is not used. Moreover, the viscous sealant material
adheres tightly to foreign objects that penetrate through a tire,
and even when a puncture opening formed through a tire by the
penetration of a foreign substance is enlarged during the running
of the tire and the foreign object dislodges through the enlarged
opening, the foreign object can pull the viscous sealant material,
which is tightly adhered to the foreign object, into the opening
and fill the hole to keep the tire completely air-tight thereby
forming a sealed tire area.
[0037] The electrically conductive tire sealing material can be
present in the tire and preferably underlies the outermost surface
of the tire, for example, the ground-contacting tread surface, the
tread shoulder area or exposed outer sidewall surface. Underlying
the outer surface of the tire can include the sealant material
being positioned between one or more component layers of the tire
or the sealant may be directly exposed to the air within the tire
body. For example, the sealing material can be positioned in the
tire between an inner liner layer and the carcass. The inner liner
layer can be the innermost layer of the tire opposite its outer
surface (i.e. the air barrier layer). In another example, the
sealing material can be positioned on the outermost or innermost
surface of an inner liner layer. In the case of it being positioned
on the innermost surface, the sealing material can be directly
exposed to the air within the tire and can function as the air
barrier layer or a portion thereof, whereas when it is positioned
on the outermost surface of an inner liner layer, it may be between
two adjacent inner liner layers or the inner liner layer and the
next adjacent layer, e.g., carcass, sidewall, belt assembly, ply,
or base rubber layer underlying the tread and optionally a portion
of the shoulders.
[0038] As described herein, the sealant material is a component in
a self-sealing pneumatic tire. As arranged in the tire, it is
contemplated that the tire has conventional components or portions,
for example, a tread cap, a tread portion, rubber base layer,
sidewalls, a support carcass, beads or bead portions, a belt or
belt assembly, one or more plies, an inner liner that may or may
not form an air barrier layer and the like.
[0039] Generally, the tire components are related to one another in
the following arrangement. The sidewalls taper radially inward from
the shoulder region of the tread portion to the beads or bead
portions, wherein a carcass underlies the tread portion and
sidewalls to provide a support structure. An inner liner layer
underlies the carcass and the sealant material can be in direct
contact with the inner liner layer. The outer surface of the tire,
and in particular, the tread cap or portion is adapted to be ground
contacting during operation.
[0040] Positioned as a component in the tire, the sealing material
can be present as a layer arranged in an interior portion of the
tire. The thickness of a layer composed of the sealant material can
be any suitable amount to impart sufficient puncture sealing
capability to the tire. The layer, for example, in an unvulcanized
form, can have a thickness in the range of 0.15 to 2 cm, 0.2 to 1.5
cm, 0.3 to 1.2 cm, 0.4 to 1 cm, or 0.5, 0.6, 0.7, 0.8 or 0.9 cm. In
a general passenger tire, the layer can preferably have a thickness
of 0.3 to 1 cm.
[0041] The sealant material can be any suitable shape or size to
provide protection from punctures. For instance, the sealant
material can extend over various areas of an interior portion of
the tire. In an example, the sealant material is positioned in the
crown region from shoulder to shoulder. In another example, the
sealant material is positioned in one or both shoulder regions and
can further extend to adjacent areas of the tire, such as the
sidewall area or a portion thereof. In yet another example, the
sealant material is positioned from bead to bead or sidewall to
sidewall in an interior portion of the tire. Preferably, at least a
portion of the sealant material provides puncture protection to the
tire crown region.
[0042] In addition to being able to seal punctures in a tire, the
tire sealing material contains particles to provide an electrically
conductive property to the tire, and particularly, to a sealed
puncture area, for example at an outer surface of the tire. The
tire sealing material preferably contains electrically conductive
particles. The electrically conductive particles and other
components of the sealing material are described below.
[0043] The tire sealing material can include those known in the
art, for example, as disclosed in U.S. Pat. Nos. 3,952,787;
4,090,546; 4,228,839; 4,396,053; 4,445,562; 4,548,687; 4,607,065
and 6,194,485. The present disclosure includes tire sealing
materials that contain electrically conductive particles to render
the tire sealing materials conductive.
[0044] The sealing material can be prepared as known in the art,
for example, as described in the above-noted patent disclosures.
For example, various ingredients of the sealant material can be
mixed together using convenient rubber mixing equipment, such as an
internal rubber mixer. The material generally has a high enough
viscosity and tack (in its unvulcanized form) to accommodate its
placement in an unvulcanized tire without significantly departing
from conventional tire building techniques.
[0045] As noted above, the electrically conductive tire sealing
material includes electrically conductive particles, for example,
electrically conductive particles that impart a conductive property
to the material to promote detection of the material within or at
the outer surface of the tire. Electrically conductive particles
can be used interchangeably with electrically conductive powder
herein. The shape of the particles can be spherical, needle shaped
or needle like, plate-like or hexagonal or appear flaky or
irregular or amorphous. Among them, to obtain excellent electrical
conductivity, the particles preferably have a spherical shape. The
electrically conductive tire sealant material can include 0.1 to 10
phr, 0.2 to 8 phr, or 0.3 to 6 phr of electrically conductive
particles or less than 2 phr, 3 phr, 4 phr or 5 phr of electrically
conductive particles. In another example, the electrically
conductive particles can be present up to 10, 8 or 5 weight percent
of the total weight of the sealant material, or in the range of 0.1
to 5, and preferably 0.2 to 2 weight percent of the total weight of
the sealant material.
[0046] The electrically conductive particles are preferably well
dispersed in the electrically conductive tire sealant material, for
example, by mixing the electrically conductive particles with
components of the material. The mixing or stirring conditions may
be appropriately selected so as to form a uniform distribution of
the electrically conductive particles in the material. For example,
the sealant materials can be obtained by mixing the rubbers and
other components with the electrically conductive particles and
other fillers, such carbon black, tackifiers, resins, curing
agents, rubber auxiliaries or the like in conventional mixers, such
as rollers, internal mixers and mixing extruders. The viscous
electrically conductive tire sealant material is capable of flowing
into a puncture opening to seal a tire and in the process the
material forms a sealed tire area at the outer surface of the tire,
e.g., the tread. A uniform distribution of the electrically
conductive particles in the sealing material can provide a portion
of the electrically conductive materials being present at the outer
surface of the tire in the sealed tire area. Presence of the
particles at the outer surface of the tire can be detectable by
various apparatuses capable of measuring electrical conductivity to
indicate whether a tire has been punctured.
[0047] The data from the apparatus can be recorded to create a
report for the tire, e.g., an inspection report. The data can
include measurements of the electrical conductivity of the sealant
material. Measured data relating to the sealant material can be
compared to electrical conductivity data of other tire components,
e.g., tread, sidewall or various areas exposed on the outer surface
of the tire. In the case the electrical conductivity of the sealant
material measured at an outer surface of the tire is greater than
other measured values of non-sealant materials at the outer
surface, or a set baseline electrical conductivity value or
threshold known to be below the conductivity of the sealant
material, that can indicate that the tire contains a sealed
puncture containing the sealant material. The damaged or punctured
tire determination and gathered data can be added to the inspection
report to notify a person (e.g., the driver) that the tire may need
to be replaced.
[0048] In one or more embodiments, the electrically conductive
particles of the sealant material can be metallic. The sealant
material may be free, substantially free or contain less than 2, 1,
0.5, 0.3, 0.2, 0.1 phr of other non-metal fillers or non-metal
electrically conductive particles, for example, carbon black or
silica materials. The electrically conductive metallic particles
can include nickel, copper (e.g., annealed), zinc, tin, iron,
aluminum, silver, brass, silver coated copper, silver coated
nickel, silver coated aluminum, silver coated tin, silver coated
gold; nickel coated copper, nickel coated silver; silvered glass;
metal coated: glass (e.g., metallized glass fibers or spheres),
ceramics, plastics, elastomers, and mica, and combinations thereof.
The particles can be metal alloys of two or more metals, or
composites in which one or more metals are coated on another metal
or carrier substrate or core. Metals that are subject to oxidation
can be used at the metallic particles, or alternatively, a
conductive corrosion-resistant coating can be applied to prevent
oxidation.
[0049] The particles employed in the sealant material are generally
conductive by virtue of having at least a surface constituted by a
metal (e.g., a noble metal), for example, silver, copper or nickel.
Preferably, the cores of the particles, for example the portions
beneath the outer surface of the particles, also contain a metal,
which can be the same metal as a surface coating, to promote a high
electrical conductivity. In the event the core is not a noble
metal, it can be another conductive metallic material.
[0050] Purity of the electrically conductive particles of the
present disclosure is not specifically limited, but preferably 90%
by weight or more, 95% by weight or more and preferably 99% by
weight or more.
[0051] In one embodiment, the electrically conductive particles can
be electrically conductive carbon black. For example, the
electrically conductive carbon black can have a DBP absorption
value of at least 250 ml/100 g and a BET surface area oft least 500
m.sup.2/g.
[0052] The electrically conductive particles can have an average
particle size in the range of 0.1 to 10, 0.2 to 5 or 0.3 to 2
microns. The average particle size of the electrically conductive
particles can be less than 5, 3, 2, 1 or 0.5 micron. In one
embodiment, the electrically conductive particles can be
nanoparticles, for example, the average particle size of the
electrically conductive nanoparticles can be in the range of 5 to
100 nanometers (nm), or less than 80, 60, 40, 20 or 10 nm.
[0053] The electrically conductive tire sealing material can
include one or more elastomers. Exemplary elastomers include,
without limitation, natural rubber, styrenebutadiene rubber,
polyisoprene, polyisobutylene, polybutadiene, isoprene-butadiene
copolymer, neoprene, nitrile rubber, butyl rubber, polysulfide
elastomer, acrylic elastomer, acrylonitrile elastomers, silicone
rubber, polysiloxanes, polyester rubber, diisocyanate-linked
condensation elastomer, ethylene propylene diene rubbers,
chlorosulphonated polyethylene, fluorinated hydrocarbons, and
combinations thereof. The terms elastomer and rubber will be used
interchangeably in this specification.
[0054] In one embodiment, the electrically conductive tire sealing
material can include at least one high molecular weight elastomer.
The high molecular weight elastomer of the present disclosure can
be any high molecular weight elastomer capable of being
cross-linked. For example, the high molecular weight elastomer can
include ethylene-propylene-diene terpolymers, polybutadiene,
partially hydrogenated polybutadiene, butyl rubber, halo butyl
rubber for example chloro- or bromo-, acrylonitrile-butadiene
copolymer, styrene butadiene copolymer, natural rubber, or cis
polyisoprene and combinations thereof. Mixtures of two or more of
the above elastomers can also be used, as can various other
conventional high molecular weight rubbers. The number average
molecular weight of the high molecular weight elastomer can be at
least 50,000, and preferably at least 100,000.
[0055] Ethylene propylene diene elastomers are preferred. Ethylene
propylene diene elastomers are desirable for applications that
involve heat, weathering and chemical exposure as well as long term
aging. The elastomers can advantageously resist becoming brittle
with age and can flex and accommodate changes in temperature. In
one example, elastomers of this type can be terpolymers of ethylene
and propylene, and a non-conjugated diene. Such elastomers can be
highly extendable, allowing high levels of fillers and plasticizers
to be added while maintaining desirable physical properties.
[0056] In another embodiment, the electrically conductive tire
sealing material can include a polymer of relatively low molecular
weight, for example, those having a number average molecular weight
of about 500 to about 5,000 and which often are liquids at room
temperature (that is 20.degree. C. to 25.degree. C.).
[0057] Various structural types of low molecular weight polymers,
preferably in liquid form, can include ethylene-propylene
copolymer, ethylene-propylene-diene terpolymer, polybutadiene,
hydrogenated polybutadiene, butyl rubber, polypropylene (e.g.,
atactic), acrylonitrile-butadiene copolymer, styrene-butadiene
copolymer, synthetic polyterpenes, thermoplastic olefins,
pentaerythritol esters of hydrogenated rosins, triethylene glycol
esters of hydrogenated rosins, vinyl toluene copolymers, alkyl
aromatics, depolymerized natural rubber, polybutenes and
combinations thereof. Because of their cost, availability and
properties the polybutenes are desirable.
[0058] Example polybutenes can have a number average molecular
weight exceeding 1,000, which can reduce migration into adjacent
tire components. Polybutenes are available under the trademark
Indopol, e.g. Indopol H-300 and Indopol H-1900. The Indopol grades
are reported to have a polymer backbone structure resembling
isobutylene and that the Indopol H-300 and Indopol H-1900 have
viscosities ranging from 627-675, to 4069-4382 centistokes,
respectively at 210.degree. F. The number average molecular weights
(Mn) of the same materials is respectively from 1,290 to 2,300, as
determined by vapor pressure osmometry.
[0059] The electrically conductive sealant material can include a
combination of low molecular weight polymer and high molecular
weight elastomer. For example, in general, from 55 to 90 phr of the
electrically conductive sealant material can be low molecular
weight polymers with from 65 or 70 phr to 90 phr being preferred.
The amount of the high molecular weight elastomer in the sealant
accordingly can be from 10 to 45 phr with from 10 phr to 15, 20, 25
or 30 phr being preferred.
[0060] Additionally, other ingredients which can be utilized to
prepare the electrically conductive tire sealant material include
one or more reinforcing agents. A suitable agent includes finely
divided carbon, such as carbon black as known in the art. Carbon
black fillers can include conventional carbon blacks, for example
the HAF, ISAF, SAF, FEF, APF type are suitable. Other examples of
carbon black include of ASTM 300, 600 or 700 grade (e.g., N326,
N330, N550). Other suitable reinforcing agents include zinc oxide,
aluminum hydrate, lithopone, whiting, clays, hydrated silicas,
calcium silicates, silicoaluminates, magnesium oxide, and magnesium
carbonate. The amount of such reinforcing agents is from 0.1 to
about 20 phr, and desirably from 1 to 20 or 1 to 10, or 5 phr.
[0061] The electrically conductive sealant material can include a
resin, which can include at least one adhesive resin. It is
contemplated that any resin known by those of skill in the art to
be compatible with the elastomers can be contained in the
electrically conductive sealant material and may be used with one
or more embodiments of the present disclosure. As may be
appreciated by those of skill in the art, a variety of different
adhesive resins or tackifying additives may be used to practice the
present disclosure. In one example, suitable resins can show a
differential scanning calorimetry (DSC) glass transition
temperature Tg between 30.degree. and 60.degree. C. and a Ring and
Ball softening point between 80.degree. and 110.degree. C.
[0062] Multiple adhesive resins can be included in the resin, such
as a mixture of phenolic resins. Adhesive resins can include
resorcinol, resorcinolic derivatives, monohydric phenols and
derivatives thereof, dihydric phenols and derivatives thereof,
polyhydric phenols and derivatives thereof, unmodified phenol
novolak resins, modified phenol novolak resin, novolak resins, and
mixtures thereof. Resins can further include petroleum hydrocarbon
resin tackifiers such as aliphatic petroleum resin, aromatic
petroleum resin (e.g., a C5-C9 aromatic modified hydrocarbon
resin), alicyclic petroleum resin and the like, or natural
tackifiers. The resin or combination of resins can be present in
the electrically conductive sealant material in a range of 0.5 and
10 phr, 1 and 8 phr or less than 6, 5, 4 or 3 phr.
[0063] The degree of crosslinking achieved with this or other
curing systems is such as to prevent general flow of the sealant
material at the high temperature experienced in the running tire
and to provide the sealant with sufficient resiliency for proper
sealant performance in the presence of an opening. Crosslinking
ingredients are included in the sealant material when the one or
more crosslinkable elastomer materials is of a type that crosslinks
on exposure to vulcanization temperatures. Examples of such
vulcanization agents are the standard accelerators utilized in the
rubber industry; such as Santocure NS
(N-Tert-butyl-2-benzothiazolesulfenamide), mercaptobenzothiazole,
tetramethylthiunam disulfide; peroxides, such as dicumyl peroxide;
and sulfur. It is preferable to use a crosslinking agent from the
quinones class, for example a quinine dioxime, such as paraquinone
dioxime. The incorporation of stearic acid and zinc oxide to assist
in the crosslinkage reaction, as is known, is also contemplated.
When present, the cross-linker or accelerator should be from 0.02
to 2.5 phr, the sulfur from 0.1 to 5 phr, the zinc oxide from 0.2
to 10 phr, the stearic acid from 0.1 to 5 phr and the peroxide from
1.0 to 10 phr.
[0064] The compositions of the present disclosure may further
include, if desired, various appropriate additional compounding
ingredients, e.g., pigments, extenders, surfactants, stabilizers
and anti-oxidants.
[0065] The sealing material can also be assembled with other tire
components as conventionally known in the art and be further
vulcanized together with the other components to form a pneumatic
tire. For instance, subsequent to the unvulcanized pneumatic tire
including the sealant material is assembled, the tire and its
components are vulcanized using a normal tire cure cycle, which can
include a range of temperatures. In an example, a tire (e.g., a
passenger tire) can be cured at a temperature in the range of
130.degree. C. to 170.degree. C. The tire can be cured for a period
of time as conventional in the art, for example, in a range of 10
to 45 minutes or more. The length of the cure period can be
dependent on the tire size and degree of desired depolymerization
of the rubber contained therein. The cure period can also be
affected by the thickness of the component layers themselves (e.g.,
the sealant material).
[0066] During use, the sealing material can fill damaged area, an
opening or puncture in the tire such that a portion of the sealing
material flows towards the outer surface of the tire thereby
exposing the components of the sealing material at the outer
surface of the tire, for example, in a sealed tire area that forms
a portion of the outer surface. That is, when the sealant material
contains electrically conductive particles, and the sealant
material flows through a puncture opening in the tire, the sealant
carries the electrically conductive particles with the flow and
results in electrically conductive particles being present at and
on the outer surface of the tire in a sealed tire area. Prior to
the sealant material flowing to the outer surface of the tire, the
outer surface would have a base or baseline electrical conductivity
and a baseline low or non-existent concentration of electrically
conductive metallic particles. Thus, when the electrically
conductive particles of the sealant material are in an interior
portion of the tire and not at the outer surface, the outer surface
of the tire should not contain uncharacteristic electrical
conductive peaks or readings above the baseline electrical
conductivity or concentration of electrically conductive particles
for tire components forming the outer surface. The electrically
conductive particles of the sealant material at the outer surface
of the tire can be detected by an apparatus to indicate that the
tire was punctured or damaged and that the sealant material has
filled the puncture or other damaged area by flowing to the surface
of the tire. The detected electric conductivity of the sealant
material or electrically conductive particles can correspond to a
reading or measurement and the readings can be compared to baseline
values for indicating the present of sealant material near or at
the outer surface of the tire. The baseline electrical conductivity
can be pre-determined for conventional tire components that
generally form the outer surface of a tire, for example, the rubber
tread or rubber sidewall components.
[0067] Electrically conductive particles of at the outer surface of
the tire can be detected by any suitable apparatus, for example, an
apparatus that can detect the presence of electrically conductive
particles or the electrical conductivity of a material (e.g. the
sealant material). As noted above, the detection or measurement of
electrical conductivity by the apparatus can be compared to a
baseline value other tire components or for the outer surface of
the tire, which can be pre-programmed into the apparatus.
Measurements can be stored in the apparatus, inclusive of the
determination of whether the tire has a sealed puncture containing
sealant material, which can be linked to a computer system to
generate an inspection report of the tire. Alternatively, the
apparatus can measure the electrical conductivity of non-sealant
material components (e.g., tread, sidewalls, bead portions,
shoulder areas, combinations thereof) to establish baseline
conductivities. Conductivities measured above the baseline values
can indicate that a portion of the electrically conductive sealant
material is present at the outer surface of the tire, for example,
in a sealed tire area in the tread area.
[0068] Examples of an apparatus for measuring electrical
conductivity can include a meter, gauge, sensor or probe, recorder
or other instrumentation. Further examples of apparatuses that can
be used to detect and measure the electrical conductivity of tire
components forming the outer surface include hand-held devices,
electrodes, probes (surface probes), voltage systems (dc voltage)
with meters (ammeter), electrical resistance meter and probe system
(2, 3, 4, 5, 6 or more), and the like.
[0069] In one embodiment, a conventional electrical-resistance
measuring device can be connected (e.g., electrical cords) to two
or more probes that can be brought into contact with parts of the
tire (e.g., bead portion and tread). Multiple measurements can be
taken to ensure accuracy, for instance, the tire can be rotated
slightly between measurements until a complete electrical
conductivity profile of the tire is obtained. To decrease
measurement times, multiple probes can be attached to various
portions of the tire to gather many electrical conductivity
measurements simultaneously.
[0070] Measuring the electrical conductivity from the bead portion
to the tread along multiple locations around circumference of the
tire can provide a baseline electrical conductivity from the
rim-contacting bead to the ground-contacting tread of the tire. In
the event of a puncture, for instance in the shoulder area or
sidewall of the tire, the electrically conductive sealant material
will flow into an open puncture area and form a sealed tire area in
a portion of the sidewall or shoulder. The presence of the
electrically conductive sealant material in the conductive path
being measured between the rim-contacting bead to the
ground-contacting tread will increase the electrical conductivity
of the path due to the presence of the electrically conductive
particles. That is, the electrically conductive sealant material
preferably has a higher electrical conductivity value than the
rubber components in the tire that form the outer surface of the
tire. As described above, the conductivity path profile and
baseline value can be compared to measurements taken in locations
that contain a portion of the electrically conductive sealant
material in the path to determine the presence of damage or a
sealed puncture area.
[0071] In another embodiment, the apparatus capable of detecting
electrical conductivity or the presence of electrically conductive
particles has a contact area. The contact area is the area on the
apparatus that is in direct contact with a material and registers a
change or value of an electrical field or conductivity. Thus, the
apparatus can be moved around the tire (e.g., the outer surface)
such that the contact area of the apparatus touches a portion or
the entire outer surface of the tire for measuring the electrical
conductivity of portions of the tire. Alternatively, the tire can
be moved within the contact area or areas of a stationary or fixed
apparatus for indicating whether the tire has a sealed puncture.
For example, one or more apparatuses can be secured in place, such
as on a detection plate or station, and a tire can be rolled into
an inspection area that positions the tire against the contact
areas of the one or more apparatuses so the tire can be inspected
for punctures by registering a change in electrical conductivity or
presence of electrically conductive metallic particles.
[0072] All references, including but not limited to patents, patent
applications, and non-patent literature are hereby incorporated by
reference herein in their entirety.
[0073] While various aspects and embodiments of the compositions
and methods have been disclosed herein, other aspects and
embodiments will be apparent to those skilled in the art. The
various aspects and embodiments disclosed herein are for purposes
of illustration and are not intended to be limiting, with the true
scope and spirit being indicated by the claims.
* * * * *